WBCS Preliminary Examination 2021 — General Studies · Question 121 of 200

Answer: (C) longitudinal and transverse

Waves on a water surface are neither purely transverse nor purely longitudinal: water particles move in roughly circular or elliptical paths, so they are displaced both up and down (transverse) and to and fro along the direction of travel (longitudinal). A motor boat's propeller also sends longitudinal pressure (sound) waves through the water below. Purely transverse waves: light, waves on a string; purely longitudinal: sound in air. Stationary (standing) waves need two identical waves travelling in opposite directions, as on a guitar string.